A sensor device for distance measurement and a function test of the sensor are discussed in German patent document DE 10 2005 057 973 A1, for example.
This document discusses a method for function testing of an ultrasonic sensor on a motor vehicle in which such a strong ultrasonic signal is emitted in a test mode that under conventional conditions this ultrasonic signal will be reflected from the ground in front of the vehicle and received again.
This is a comparatively “rough” test.